Granular inert carriers have been heretofore used to carry pesticide, herbicide, fungicide and fertilizer formulations. These carriers have been broadly categorized as inorganic and botanical by Ross, H. W., "Available Granual or Carriers--Properties and General Processing Methods", Pesticide Formulations and Application Systems: Second Conference, ASTM STP 795, K.G. Seymour, Ed., American Society for Testing Materials, 1983, pp. 32-44. The inorganic category comprises clays, sand and vermiculite. While low in cost, the clays oftentimes need to be treated with a deactivator prior to formulation to prevent decomposition of the active ingredient.
The botanical category comprises corn cobs, walnut shells, rice hulls, and wood. Corn cobs have been a primary source of inert granular carriers, but continued expansion of the use of combine harvesters and occasional drought conditions have raised questions as to the adequacy of supply of corn cobs and have driven up its cost.
The botanical carriers, along with the low-volatile matter clays, sand, and vermiculite all break down slowly, or not at all, when applied to the soil. As a result, intact granules containing active ingredients of pesticide, herbicide, and fertilized fungicide may remain available for long periods of time on the soil surface. This has resulted in reports of bird kills and subsequent action by the Environmental Protection Agency (EPA) to ban, or severely restrict, the use of some products to mitigate this problem. Thus, an inert carrier which could maintain its integrity during formulation but disintegrate when wetted by rainfall or irrigation conditions after application would be advantageous in reducing the likelihood of birds ingesting unwanted materials.
However, in some circumstances it may be desirable to maintain the integrity of the substrate on the ground, even when subjected to wetting conditions. Accordingly, there has been a demand for an improved granular carrier which can have controlled disintegration for utilization under varying ground or soil conditions while offering protection against avian toxicity when desired.
A principle object of this invention is, therefore, to provide an improved inert granular substrate for carrying pesticide, herbicide, fungicide and/or fertilizer formulations.
A more particular object of the invention is the provision of an inert, granular substrate for carrying pesticide, herbicide, fungicide and fertilizer formulations, the disintegration of which is controllable.
A still more particular object of the invention is the provision of an organic, biodegradable granular substrate which maintains its integrity when dry, but readily disperses on the ground when subjected to wetting conditions.
A further object of the invention is the provision of an inert granular substrate, which is organic and biodegradable but which can readily disperse on the ground when subjected to wetting as by rainfall or irrigation.
Another object of the invention is the provision of an inert, granular substrate which is more economical than corn cobs, and which can be prepared from grain dust and grain hulls.
Still another object of this invention is the provision of an improved method for making an inert, granular substrate for carrying pesticide, herbicide, fungicide and fertilizer formations.
Still another and additional object of the invention is the provision of an improved method for making an inert, granular substrate under controlled conditions which permits adjustment of the rate of disintegration of the substrate on the ground under wetting conditions.
Further objects and advantages of the invention will become apparent by reference to the following description.